Let me start by saying that this movie is just plain wrong and just plain kick-ass in equal proportions.  You’ll spend an hour and a half saying "Oh no they won’t", "Oh no they didn’t", or "Oh God, they did".  You’ll say it about the gunfights just as much as you’ll say it about the plot, which is just as thin as it ought to be in a movie called "Shoot ’em Up".  It’s just enough story to explain the way to the next outrageously implausible situation.  Think "Kill Bill" with guns.  And that’s as it should be.  The villains are reeealy villainous.  You can’t possibly like them, and in true shoot-em-up fashion, they possess a seemingly bottomless supply of hapless, innacurate bodyguards, thugs, and other nameless red-shirt equivalents.  They’re so numerous, anonymous, and short-lived that I’m fairly certain a detailed analysis of the eventual DVD release will find the same stuntmen dying at least a dozen times apiece.

Our anti-hero isn’t merely hard-boiled, he’s completely solidified.  He’s so hard-core implacable that we don’t even get to learn his name.  No doubt about it, the James Bond folks are regretting the day they passed over Clive Owen for Daniel Craig, and Owen couldn’t have asked for a better "Up yours!" than this.  He’s a one-man killing machine, pissed off at the world in general and pretty much everyone in it individually.  He runs rich, inconsiderate drivers off the road for not using their turn signals, shoots bad guys in the foot for having ugly toenails, and shoots the ponytail off the back of a thug’s head because he thinks it looks stupid (I have some personal issue with that one).

As one of the few characters in the movie with a name, Paul Giamatti’s "Mr. Hertz" manages to be suitably evil.  More evil than he has been before.  Oh he’s been slimy before, sure, but this time he’s just plain evil.  He’s smug, he’s mean, he’s callous.  You hate him right away, and you spend the whole film wanting him to die.  But you really enjoy hating him because, for the first time in the history of film, there’s a villain intelligent enough to make the observation "Do we suck?  Or is he really that good?"  He’s even intelligent enough not to reveal any big secrets during his character’s obligatory exposition scene.  Overall, it’s an awesome job by Mr. Giamatti.  He’s portrayed a total caricature of a human being and somehow made him believable.

As for the gunfights… Even though it seems like they make up approximately 85% of the film, they don’t get old or tedious.  They are always new and inventive, and each one tops its predecessor in terms of style, ingenuity, and scale.  Just when you think a gunfight can’t get any weirder, it does.  It’s like a team of writers were placing bar bets, trying to out-do each other.

Writer 1: "I bet I can write a scene where the hero shoots people while holding a baby."
Writer 2: "Oh yeah, well I’ll write a scene where he shoots people while MAKING a baby, if you know what I mean (heh heh)."
Writer 3: "I’ll do better than that.  I’ll write a scene where he shoots people while DELIVERING a baby."
…
(Long pause)
…
Writer 1 & 2 (in unison): "Name that tune, dude!"

You think I’m making this up, don’t you.  No I’m not.  He really does those things.  And then it’s like the producer came along and upped the ante on them even more:

Producer: "Oh, so you think you guys are good, huh?  Well how’s this.  No fireballs.  You can’t blow up any cars, buildings, gas-tanks, nothing.  You may only flip one car, and… uh… let’s see… something hard.  I’ve got it!  The hero must kill at least two bad guys using only a carrot.  In fact, while you’re at it, I want you to make carrots an integral part of every scene… I just bought a carrot farm and I need to look out for my investment."
Writer 1: "Dude, you’d better be buying us pizza."
Writer 2: "And beer."
Writer 3: "As in "keg of"."

This is not high art.  This is not meant to be high art.  This is high body count, plain and simple.  A couple of bad guys even get killed by the credit sequence.  I’m not kidding, they don’t just get killed in the credit sequence, they actually get killed by the credits themselves.  What more could you want?  Four stars, Mel-bob sez check it out.